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Ubuntu Security Notice USN-6881-1
July 08, 2024

exim4 vulnerability

A security issue affects these releases of Ubuntu and its derivatives:

• Ubuntu 20.04 LTS
• Ubuntu 18.04 LTS
• Ubuntu 16.04 LTS
• Ubuntu 14.04 LTS

Summary:

Exim could be made to allow response injection if it received a specially
crafted response.

Software Description:

• exim4: Exim is a mail transport agent

Details:

It was discovered that Exim did not enforce STARTTLS sync point on client
side. An attacker could possibly use this issue to perform response
injection during MTA SMTP sending.

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 20.04 LTS
exim4 4.93-13ubuntu1.11
exim4-base 4.93-13ubuntu1.11
eximon4 4.93-13ubuntu1.11

Ubuntu 18.04 LTS
exim4 4.90.1-1ubuntu1.10+esm4
Available with Ubuntu Pro
exim4-base 4.90.1-1ubuntu1.10+esm4
Available with Ubuntu Pro
eximon4 4.90.1-1ubuntu1.10+esm4
Available with Ubuntu Pro

Ubuntu 16.04 LTS
exim4 4.86.2-2ubuntu2.6+esm7
Available with Ubuntu Pro
exim4-base 4.86.2-2ubuntu2.6+esm7
Available with Ubuntu Pro
eximon4 4.86.2-2ubuntu2.6+esm7
Available with Ubuntu Pro

Ubuntu 14.04 LTS
exim4 4.82-3ubuntu2.4+esm8
Available with Ubuntu Pro
exim4-base 4.82-3ubuntu2.4+esm8
Available with Ubuntu Pro
eximon4 4.82-3ubuntu2.4+esm8
Available with Ubuntu Pro

In general, a standard system update will make all the necessary changes.

References:
https://ubuntu.com/security/notices/USN-6881-1
https://ubuntu.com/security/notices/USN-6881-1
CVE-2021-38371

Package Information:
https://launchpad.net/ubuntu/+source/exim4/4.93-13ubuntu1.11
https://launchpad.net/ubuntu/+source/exim4/4.93-13ubuntu1.11